Her office says she will not be at a scheduled appearance alongside husband William at Wednesday's London movie premiere of The Hobbit – following her cancelation of two events that had been planned for last weekend.

Experts on her condition, hyperemesis, or HG, are not surprised that she is still struggling, because her departure from King Edward VII hospital did not signal she has beaten it.

"Calling it acute morning sickness gives the impression that it is a short-term thing," says Caitlin Dean, a former HG sufferer and spokeswoman for Pregnancy Sickness Support.

"It's not like she recovered from it – it's an ongoing thing," says Dean. "Realistically, there won't be significant recovery until 12 weeks at the minimum. It could be 16 plus weeks. The more severe it is, the longer it can go on for."

Dr. Dagni Rajasingam, a practicing obstetrician and a spokesperson for the Royal College of Obstetricians, concurs, saying, "It could come back in waves. It can come back unpredictably relatively soon or weeks after."

The couple's office at St. James's Palace announced Tuesday that Kate "will continue to rest privately." Although she left London's King Edward hospital VII for her cottage home at Kensington Palace, palace officials won't confirm if she is there now.

Dean says of Kate's condition, which can require constant bed-rest: "You know you have to try to eat and try to drink, but it is easier said than done, because the nausea is absolutely constant."